System and method for communication session correlation

ABSTRACT

A system and method for correlating communication sessions. A globally unique correlation identifier is created and exchanged between the parties during Session Initiation Protocol (SIP) session setup to allow for association and correlation of additional SIP sessions between the same parties or with additional parties. The correlation information may then be used by network and session entities to perform different services.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/153,604 filed Jun. 6, 2011, which is a continuation of U.S.patent application Ser. No. 11/549,746 filed Oct. 16, 2006, now U.S.Pat. No. 7,983,240, the disclosures of which are fully incorporatedherein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to communication systems. Moreparticularly, and not by way of limitation, the invention is directed toa system and method for correlating different communication sessions.

Correlation is a mathematical term for a statistical measurement on thedegree of dependency of two variables. In mathematics, a correlationcoefficient is used to indicate the strength and direction of a linearrelationship between two random variables. In communication systems, itis desirable to know whether two or more sessions used to set up mediastreams are correlated in some sense (for example, in the sense thatthey are used in the same context). Such sessions may be set up andoperated under the Session Initiation Protocol (SIP) or other suitablecommunication protocol. On the terminal side, such a correlation couldmean, for example, displaying text from a chat session and video fromanother session in the same terminal window. On the network side, itcould mean, for example, applying some special charging scheme to amulti-service session comprised of two or more individual sessions.

In order to provide these and similar services, it must be determinedand communicated how sessions relate to each other. However, there is noinherent mechanism in today's networks that provides the capability toindicate correlation between SIP sessions. Rather, higher levelapplications utilizing multiple SIP sessions must correlate the sessionsat the application level using information available to each particularapplication. Due to the lack of inherent correlation mechanisms,however, the application level correlations may lead to falsecorrelation assumptions.

What is needed in the art is a system and method for correlatingdifferent communication sessions which overcomes the shortcomings of theprior art. The present invention provides such a system and method.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a system and method for correlatingcommunication sessions. The invention creates and exchanges between theparties, a globally unique correlation identifier during SIP sessionsetup to allow for association and correlation of SIP sessions. Thecorrelation information may then be used by network and session entitiesto perform different services.

Thus, in one aspect, the present invention is directed to a method ofcorrelating different communication sessions. The method includescreating a globally unique correlation identifier during establishmentof a first communication session between a first entity and a secondentity; storing the correlation identifier by the first and secondentities; and utilizing the correlation identifier to correlate with thefirst session, a subsequent session established between the first andsecond entities.

In another aspect, the present invention is directed to a system forcorrelating different communication sessions. The system includes meansfor creating a globally unique correlation identifier duringestablishment of a first communication session between a first entityand a second entity; means for storing the correlation identifier by thefirst and second entities; and means for utilizing the correlationidentifier to correlate with the first session, a subsequent sessionestablished between the first and second entities.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

In the following, the essential features of the invention will bedescribed in detail by showing preferred embodiments, with reference tothe attached figures in which:

FIG. 1 is a signaling diagram illustrating the flow of messages betweenvarious network entities when establishing a SIP session utilizing aSame-Session (SS) header in accordance with the teachings of the presentinvention;

FIG. 2 is a signaling diagram illustrating the flow of messages betweenvarious network entities when establishing a P2P session with anintermediary in accordance with the teachings of the present invention;

FIGS. 3A-3D are portions of a signaling diagram illustrating the flow ofmessages between various network entities when performing thecorrelation process in a group communication case in accordance with thepresent invention; and

FIG. 4 is an illustrative drawing illustrating a correlation structurebetween several communication sessions at a high level of abstraction.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a system and method for correlatingcommunication sessions. The invention creates and exchanges between theparties, a globally unique correlation identifier during SIP sessionsetup to allow for association and correlation of SIP sessions. Thecorrelation information may then be used by network and session entitiesto perform different services. It should be noted that sessions may beconducted between fixed terminals, mobile terminals, user agents,network nodes, and the like. The term “entities” is used herein toencompass all terminals, agents, nodes, and the like that may be partiesto sessions. This invention is also described in S. Loreto et al., “TheSession Initiation Protocol (SIP) Dialog Correlation”, IETF SIPPINGWorking Group Internet Draft, Jun. 25, 2006, which is incorporated byreference herein in its entirety. This draft is available online athttp://tools.ietf.org/wg/sipping/draft-loreto-sipping-dialog-correlation-01.txt.

In an exemplary embodiment, the present invention communicates acorrelation identifier (ID) in a new header with the label“Same-Session” added to the SIP INVITE and REFER messages. In oneembodiment, the correlation ID may be communicated between two useragents (UAs) in a simple point-to-point (P2P) scenario in which both UAshave all the information required to uniquely identify the dialog(Call-ID, From-Tag, and To-Tag) with one correlation ID. In otherembodiments addressing the use of intermediaries (for example abusiness-to-business (B2B) UA, group communications, and use of multiplecorrelation IDs, the correlation ID may be sent to multiple entities.

In the preferred embodiment, the invention creates and exchanges aglobally unique correlation ID during IP Multimedia Subsystem (IMS)session establishment. The exchange of the globally unique correlationID provides the ability to associate and correlate independent IMSsessions (for example, SIP sessions). The correlation IDs may betransported in a SIP header field.

The preferred embodiment for the correlation ID is a value comprising anumber of attributes derived from the SIP session. In the P2P case, thecorrelation ID preferably includes three parameters: Call-ID, To-Tag,and From-Tag. Although the Call-ID and From-Tag make the correlation IDglobally unique on their own, the To-Tag is needed to address thescenario of forking proxies in the path of signaling. Thus, the P2Pcorrelation ID may take the form:

-   -   Same-Session: Call-Id; From-Tag; To-Tag

For example, the P2P correlation ID may appear as:

-   -   Same-Session: 3s09cs03; ty20s; d92119.

In the P2P case, the Call-ID and From-Tag are derived from the INVITErequest, and the To-Tag is derived from the 200 OK response to therequest. For example in a session setup request, the Call-ID, From-Tag,and To-Tag may appear as:

INVITE sip:alice.doe@home1.net SIP/2.0 From:<sip:elisa.coya@example.net>;tag=ty20s To: <sip:alice.doe@home1.net>Call-ID: 3s09cs03

The response message may include the following fields:

SIP/2.0 200 OK From: <sip:elisa.coya@example.net>;tag=ty20s To:<sip:alice.doe@home1.net>;tag=d92119 Call-ID: 3s09cs03

In the case of an intermediary (e.g., a B2B UA) inside the signalingpath between the two UAs, additional logic is required, both in the UAsand in the B2B UA. This enables the exchange of the aforementionedinformation between the two independent sessions established by theintermediary with two communication partners.

In the intermediary case, the Call-ID is different on the receiving andtransmitting sides of the intermediary. For example, the two Call-IDsmay take the form:

Same-Session: Focal Point URI Same-Session: conf123@factory.domainA.org

In the group communication cases, the correlation ID may include asingle focal point URI, which is inherently unique and is assigned bythe conference factory during conference creation. The focal point URIis used to create the correlation ID. The correlation ID is uniquebecause the conference factory assigns unique URIs to each newconference instance. The focal point URI is communicated to the creatorof the conference during the conference creation process (in the contactheader of the 200 OK).

In a dial-in conference scenario, a REFER request is then submitted fromthe creator of the conference to the other participant(s). TheSame-Session header in the REFER request contains the focal point URI asthe correlation ID as described above. In this case, the correlation IDvalue is inserted in the Refer-to header.

If the invitation is accepted, the receiver of the REFER request thenissues an INVITE request to the focal point containing the samecorrelation ID in the Same-Session header.

In a dial-out scenario the procedure is the same with the exception thatthe REFER request is sent to the focal point responsible for issuing theINVITE request(s).

For example, a conference creation request sent to a conference factorymay take the form:

INVITE sip:conf_fact@domainA.org SIP/2.0 From:<sip:ueA@domainA.org>;tag=ty20s To: <sip:conf_fact@domainA.org>

A response to the conference creation request containing a focal pointURI may take the form:

SIP/2.0 200 OK From: <sip:ueA@domainA.org>;tag=ty20s To:<sip:conf_fact@domainA.org>;tag=d92119 Contact:<sip:conf123@factory.domainA.org>

A REFER message containing the correlation ID (focal point URI) may thentake the form:

REFER sip:b@domainB.org SIP/2.0 From: <sip:a@domainA.org>;tag=193402342To: <sip:b@domainB.org> Contact: <sip:a@domainA.org> Refer-To:conf456@factory.domainA.org?Same- Session=conf123@factory.domainA.org;text Same-Session: conf123@factory.domainA.org

The present invention includes a method of correlating independent IMSsessions in independent correlation groups. During the establishment ofa new session, a new correlation ID is created and used. If the newsession should be correlated with an existing session, the correlationID of the existing session is used. All sessions using the samecorrelation ID are considered to be correlated.

FIG. 1 is a signaling diagram illustrating the flow of messages betweenvarious network entities when establishing a SIP session utilizing aSame-Session (SS) header in accordance with the present invention.During the establishment of the first, new, session (not to becorrelated with an existing session), UE-A 11 populates the Same-Sessionheader of the INVITE message 12 with two out of three of the correlationID parameters (i.e., the Call-ID and the From-Tag). The third parameter(i.e., the To-Tag) is created by UE-B 13 and is included in the 200 OKresponse message 14. Once the establishment procedure is complete, bothparties may store the correlation ID in a local correlation table orother mapping construct (e.g., table, hash, and the like) and may usethe correlation ID when establishing future sessions. The session, inthis example a chat session 15, is then established.

An exemplary mapping table is shown in Table 1 below. The mapping tableis used to associate correlation IDs with session IDs. Additionalentries such as the media type may be included, but are not required formapping purposes.

TABLE 1 Correlation ID Dialogue ID Call-ID1, From-Tag1, To-Tag1Call-ID1, From-Tag1, Chat session To-Tag1 Call-ID1, From-Tag1, To-Tag1Call-ID2, From-Tag2, VoIP session To-tag2

Still referring to FIG. 1, at some later point in time, UE-B 13 adds aVoIP component to the ongoing chat by establishing a new SIP session. Inorder to correlate the new session to the existing one, UE-B uses thedialogue ID (i.e., session identifier) of the ongoing chat session as akey to perform a search in the correlation table and fetch thecorrelation ID for use in the correlation procedure. UE-B places thecorrelation ID in a Same-Session header of the INVITE message 16 andsends it to UE-A 11.

Upon receiving the INVITE message 16 with the Same-Session headercontaining a complete correlation ID (i.e., with all three parameters),UE-A 11 interprets this as a session that should be correlated with anexisting session. UE-A then accesses its correlation table to find amatch for the correlation ID received. If a match is found, it meansthat UE-A is already part of an ongoing session to which the correlationID points. The new, now correlated session, is inserted as a new entryin the table. If a match is not found, UE-A may add the correlation IDto the table, thereby acknowledging the correlation to an existingsession in which it (UE-A) is not involved. UE-A accepts in a 200 OKmessage 17, and the P2P voice session is established and correlated withthe P2P chat session at step 18. Alternatively, UE-A may reject therequest.

FIG. 2 is a signaling diagram illustrating the flow of messages betweenvarious network entities when establishing a P2P session with anintermediary B2B UA 21 in accordance with the present invention. In theevent of an intermediary to the P2P flow, the two peers (UE-A 11 andUE-B 13) are not directly connected. Instead, there are two differentsessions, one between the intermediary and each respective peer.Therefore, additional logic is required to correlate the sessions. Forexample, if a B2B UA is placed between the two peers, there are certainfunctionalities required for the generation of the correlation ID.

The B2B UA shall:

-   -   22: Receive on first leg at UAS, an INVITE from UE-A directed to        UAC    -   23: Copy from server to client side (INVITE): SS information,        From header, and To header    -   24: Send INVITE from UAC to UE-B on second leg    -   25: Receive 200 OK from UE-B    -   26: Re-use To-Tag value in the correlation-ID from client to        server side (200 OK)    -   27: Send 200 OK from UAS to UE-A on first leg.

The correlation table in this scenario is created and populated in thesame way as shown in Table 1 above.

In the case of group communication via a focal point, the correlation IDcan be created using the focal point URI. To be able to communicate acommon correlation ID to participants of a conference, the correlationID is included in the REFER request transmitted either to theparticipant (dial-in) or to the focal point (dial-out). The correlationID may be included in full in the REFER request. Further, it is requiredthat the receiving party copy the Same-Session header value in the REFERto the Same-Session header of the subsequent INVITE message.

Table 2 below is a correlation table illustrating a scenario in whichtwo communication parties have established one chat and one VoIP sessionbetween them via two focal points. Note that the URI of the first focalpoint is used to create the correlation ID, which is used also forcorrelation of the second session. Moreover, in a potential case of bothsessions traversing the same focal point, the table would be identical.

TABLE 2 Correlation ID Dialogue ID conf123@factory.domainA.org Call-ID1,From-Tag1, Chat session To-Tag1 conf123@factory.domainA.org Call-ID2,From-Tag2, VoIP session To-tag2

Additional intermediaries between the communication partners (e.g., theUAC and the focal point(s)) should be transparent to the communication.This means that the content of the Same-Session header should be copiedfrom one side of a B2B UA to the other.

FIGS. 3A-3D are portions of a signaling diagram illustrating the flow ofmessages between various network entities when performing thecorrelation process in a group communication case in accordance with thepresent invention. A precondition for FIGS. 3A-3D is that a chat sessionis ongoing between UE-A 11, UE-B 13, and UE-C 30. The correlation ID(conf123@chat-factory.domainA.org) is stored on all terminals.

At step 31, UE-A 11 adds a VoIP component to the group chat and invitesUE-B 13 to participate. UE-A retrieves from its correlation table, thecorrelation ID to be used for the VoIP session. UE-A adds thecorrelation ID to the Same-Session header of the INVITE message 7.Later, UE-A again includes the correlation ID in the Same-Session headerof the REFER message 9 sent to UE-B. UE-B copies the Same-Session headerfrom the REFER message into the INVITE message 10, which is returned,signifying UE-B's acceptance. In this manner, the chat session betweenUE-A, UE-B, and UE-C is correlated with the VoIP session between UE-Aand UE-B.

The present invention also includes a method of creating and identifyingcorrelation subsets for independent IMS sessions. The correlationapproach described in FIGS. 1, 2, and 3A-3D is based on the principle ofcorrelation groups identified through a single correlation ID. Thismethodology does not foresee the correlation of a new session with asubset of an existing group of correlated sessions.

According to the procedure described in FIGS. 1, 2, and 3A-3D, a newsession can join a group of correlated sessions by sharing itscorrelation ID. As an enhancement to the aforementioned basic solution,correlation subgroups may be formed. This enhancement does not requireadditional data to be available to the parties involved in thecorrelation.

The procedure for the establishment of the first session andcreation/communication of the correlation ID is identical to the basiccorrelation approach. Subsequently, during establishment of a secondsession to be correlated with the first session, a new correlation ID iscreated in accordance with the procedures previously described. Thisadditional correlation ID may be communicated in different ways usingthe Same-Session header field. First, a single header may be utilizedcontaining multiple correlation IDs separated by commas. An example ofthis approach is:

Same-Session: Correlation ID1, Correlation ID2 Same-Session:Call-Id1;From-Tag1;To-Tag1,Call-Id2;From-Tag2;To-Tag2 Same-Session:3s09cs03;ty20s;d92119, 4d10dr04;hg30k;e872k8

Alternatively, multiple headers may be utilized, each with a singlecorrelation ID. An example of this approach is:

SameSession: Correlation ID1 SameSession: Correlation ID2 SameSession:Call-Id1;FromTag1;ToTag1 SameSession: Call-Id2;FromTag2;ToTag2SameSession: 3s09cs03;ty20s;d92119 SameSession: 4d10dr04;hg30k;e872k8

When individual correlation IDs are carried in multiple headers, theorder may be fixed. For example, the value of the first header may beused to indicate the correlation ID of the higher-level session whilethe value of the second header may be the correlation ID for the newsession.

The use of the Same-Session header in the communication flow isanalogous to the approach presented in FIGS. 1, 2, and 3A-3D. Here,however, all but the last correlation IDs are already formulated (at thetime of establishment of the new session) and inserted in previousSame-Session header(s). The new correlation ID is created as describedabove and inserted in the new Same-Session header field.

Table 3 below is an exemplary correlation table for the scenario inwhich two users (A and B) establish three sessions correlated in twosubgroups. The correlation table is maintained by the clients.

TABLE 3 Correlation ID Dialogue ID Call-ID1, From-Tag1, To-Tag1Call-ID1, From-Tag1, To-Tag1 Chat Call-ID1, From-Tag1, To-Tag1,Call-ID2, From-Tag2, To-Tag2 VoIP Call-ID2, From-Tag2, To-Tag2 Call-ID2,From-Tag2, To-Tag2, Call-ID3, From-Tag3, To-Tag3 Video Call-ID3,From-Tag3, To-Tag3

FIG. 4 is an illustrative drawing illustrating a correlation structurebetween four sessions 36-39 at a high level of abstraction. At thislevel of abstraction, x, y, z, and w represent different correlationIDs. The chat session 36 is correlated with the VoIP session 38 and withthe data session 39 using the “x” correlation ID. The Video session 37is correlated with the VoIP session 38 using the “y” correlation ID.However, the Video session 33 and the chat session 36 are not correlatedbecause they do not share a common correlation ID.

The present invention also includes a method of modifying thecorrelation ID of an already established session. A further extension tothe basic case is to provide the ability to modify the correlation ID ofan already established and correlated session. The goal is to modify thecorrelation table content accordingly. This requires transport of thenew correlation ID to the correlation parties along with an instructionto change the previous correlation ID in each party's correlation table.In the context of SIP/IMS, this result may be achieved by sending are-INVITE for an ongoing session, or by sending another SIP message (forexample, MESSAGE, INFO, and the like) within or outside of the ongoingsession.

Transporting the information in a SIP MESSAGE method requires theformulation of a request to change the correlation-ID. The request istransported as content by the SIP MESSAGE either within the body of themessage or in an additional header (for example, the Same-Sessionheader). The following example illustrates such signaling:

MESSAGE sip:user2@domain.com SIP/2.0 Max-Forwards: 70 From:sip:user1@domain.com;tag=49583 To: sip:user2@domain.com Call-ID:asd88asd77a@1.2.3.4 CSeq: 1 MESSAGE Content-Type: text/plainCorrelationChange: 3s09cs03;ty20s;d92119 → 4d10dr04;hg30k;e872k8

A response (e.g., 200 OK) indicating the result of the change proposalleads to a change in the correlation table of the sender.

The present invention thus provides a system and method for correlatingindependent IMS sessions.

It should be noted that the present invention correlates two or moresessions between two or more entities. There may be multiple entities inone correlation “group” and each entity may further be residing inseparate correlation groups with separate correlation IDs. For example,two P2P sessions may be established, a first session between entity Aand entity B, and a second session between entity A and entity C. Bothsessions may utilize the same correlation ID. In this case, thecorrelation allows entity A to perform intelligent actions with thisinformation. Entity C and entity B are not aware of the other session.Further, entity B and entity C may be part of other correlations withother sessions. For example, entity B may conduct another session withentity C or with entity D utilizing a different correlation ID.

Correlation IDs may also be utilized to form subgroups between differententities. In the basic case, a single correlation ID is shared by allsessions in the correlation group. In an advanced case, a newcorrelation ID is created for every new session and the correlation IDsare concatenated to signify a correlation group. For example, entity Amay start a session with entity B utilizing correlation ID (X). Entity Cthen connects to entity B and creates a new correlation ID (Y). Byconcatenating X and Y (X,Y) a correlation ID is formed which signifies acorrelation group including both the A-B session and the B-C session. Ifa fourth party wishes to establish a session, it can choose to correlatewith either (X) or (Y) or (X,Y). It may also set up a totally newcorrelation ID (Z).

Although preferred embodiments of the present invention have beenillustrated in the accompanying drawings and described in the foregoingDetailed Description, it is understood that the invention is not limitedto the embodiments disclosed, but is capable of numerous rearrangements,modifications, and substitutions without departing from the scope of theinvention. The specification contemplates any all modifications thatfall within the scope of the invention defined by the following claims.

What is claimed is:
 1. A method of correlating different end-to-end datasessions, said method comprising: creating a globally unique correlationidentifier during establishment of a first end-to-end data sessionbetween a first party and a second party, wherein the first party sendsa first portion of the correlation identifier including a Call-ID and aFrom-Tag to the second party in a Same-Session header of a SIP INVITEmessage, and the second party adds a second, completing portion of thecorrelation identifier to the first portion and sends the completedcorrelation identifier to the first party in a SIP 200 OK messageresponsive to the SIP INVITE message, wherein the second portionincludes a To-Tag which uniquely identifies the second party; locallystoring the correlation identifier by the first and second parties,wherein each party stores the correlation identifier in a local mappingunit that maps correlation identifiers to session identifiers, saidmapping unit being selected from a group consisting of a correlationtable, a hash function, and a mapping function; and utilizing thecorrelation identifier by the first or second party to correlate withthe first end-to-end data session, a second, independent end-to-end datasession subsequently established by the first or second party.
 2. Themethod according to claim 1, wherein the step of utilizing thecorrelation identifier to correlate the first and second end-to-end datasessions includes: receiving a complete correlation identifier in asetup message during establishment of the second end-to-end datasession; accessing the local mapping unit to find a match for thereceived complete correlation identifier; when the match is found,associating a session identifier for the second end-to-end data sessionwith the found correlation identifier in the local mapping unit; andwhen the match is not found, storing the session identifier for thesecond end-to-end data session and the received complete correlationidentifier in the local mapping unit.
 3. The method according to claim1, wherein the second end-to-end data session is established between thefirst and second parties.
 4. The method according to claim 1, whereinthe second end-to-end data session is established between the firstparty and a third party, wherein the first and second end-to-end datasessions are correlated as a group of sessions.
 5. The method accordingto claim 1, wherein the first end-to-end data session is apoint-to-point (P2P) session and an intermediary is interposed betweenthe first party and the second party, said intermediary conducting afirst P2P session with the first party and a second P2P session with thesecond party, and wherein the correlation identifier is createdutilizing the Call-ID, the From-Tag, and the To-Tag, wherein theintermediary forwards the Call-ID and the From-Tag to the second partyin the SIP INVITE message, and forwards the To-Tag to the first party inthe SIP 200 OK message.
 6. The method according to claim 1, wherein thestep of creating the globally unique correlation identifier includescreating the globally unique correlation identifier for a groupcommunication session utilizing a unique focal point identifiercommunicated to the first party by a conference factory while creating aconference.
 7. The method according to claim 6, wherein the globallyunique correlation identifier is communicated to all participants of theconference by including the globally unique correlation identifier in aREFER request transmitted from the first party to each participant in adial-in conference, and to a focal point in a dial-out conference. 8.The method according to claim 1, further comprising modifying theglobally unique correlation identifier, said modifying step including:creating a new correlation identifier; sending the new correlationidentifier to the first and second parties along with an instruction tochange the globally unique correlation identifier to the new correlationidentifier; and storing the new correlation identifier by the first andsecond parties.
 9. The method according to claim 8, wherein the step ofsending the new correlation identifier to the first and second partyincludes sending the new correlation identifier and the instruction in aSIP message selected from a group consisting of a re-INVITE message forthe first or second end-to-end data session, a MESSAGE message, and anINFO message.
 10. A method of correlating different end-to-end datasessions, said method comprising: establishing a first end-to-end datasession between a first party and a second party; creating a firstglobally unique correlation identifier (X) during establishment of thefirst end-to-end data session, wherein the first party sends a firstportion of the first globally unique correlation identifier including aCall-ID and a From-Tag to the second party in a Same-Session header of aSIP INVITE message, and the second party adds a second, completingportion of the first globally unique correlation identifier to the firstportion and sends the completed first globally unique correlationidentifier to the first party in a SIP 200 OK message responsive to theSIP INVITE message, wherein the second portion includes a To-Tag whichuniquely identifies the second party; locally storing the first globallyunique correlation identifier (X) by the first and second parties,wherein each party stores the first globally unique correlationidentifier in a local mapping unit, said mapping unit being selectedfrom a group consisting of a correlation table, a hash function, and amapping function; establishing a second, independent end-to-end datasession between the second party and a third party; creating by thesecond and third parties, a second globally unique correlationidentifier (Y) during establishment of the second, independentend-to-end data session; and sending the second globally uniquecorrelation identifier (Y) from the second party to the first party; andconcatenating by the first, second, and third parties, the first andsecond globally unique correlation identifiers to form a thirdcorrelation identifier (X,Y) which identifies a correlated group ofindependent end-to-end data sessions.
 11. The method according to claim10, further comprising: establishing a third, independent end-to-enddata session between the first party and a fourth party, wherein thefourth party determines whether to form a correlated group ofindependent end-to-end data sessions by selecting a correlationidentifier for the third, independent end-to-end data session from agroup consisting of: the first globally unique correlation identifier(X); the second globally unique correlation identifier (Y); the thirdcorrelation identifier (X,Y); and a fourth correlation identifier (Z).12. The method according to claim 11, wherein the correlationidentifiers are transported to each party in a single Same-Sessionheader.
 13. The method according to claim 11, wherein the correlationidentifiers are transported to each party in a plurality of Same-Sessionheaders.
 14. A system for correlating different end-to-end datasessions, said system comprising: a first communication device; and asecond communication device in communication with the firstcommunication device; wherein each of the first and second communicationdevices includes: a local mapping unit configured to map correlationidentifiers to session identifiers, the mapping unit being selected froma group consisting of a correlation table, a hash function, and amapping function; and a processor configured to cause the first andsecond communication devices to create a globally unique correlationidentifier during establishment of a first end-to-end data sessionbetween the first and second communication devices; wherein the firstcommunication device is configured to send a SIP INVITE message to thesecond communication device during establishment of the first end-to-enddata session, wherein the first communication device is configured toinclude a Call-ID and a From-Tag in a Same-Session header of the SIPINVITE message; wherein the second communication device is configured toadd a second, completing portion of the globally unique correlationidentifier to the first portion and to send the completed globallyunique correlation identifier to the first communication device in a SIP200 OK message responsive to the SIP INVITE message, wherein the secondportion includes a To-Tag which uniquely identifies the secondcommunication device; wherein the first and second communication unitsare configured to store the globally unique correlation identifier intheir local mapping units and to utilize the stored globally uniquecorrelation identifier to correlate with the first end-to-end datasession, a second, independent end-to-end data session subsequentlyestablished by the first communication device or the secondcommunication device.
 15. The system according to claim 14, wherein whenthe second, independent end-to-end data session is established, thelocal correlation unit of the second or first communication device isconfigured to receive from the first or second communication device,respectively, a query including the globally unique correlationidentifier, and to associating a session identifier for the secondend-to-end-data session with the globally unique correlation identifier.16. The system according to claim 14, wherein the second end-to-end-datasession is established between the first and second communicationdevices.
 17. The system according to claim 14, wherein the secondend-to-end-data session is established between the first communicationdevice and a third communication device, wherein the first and secondend-to-end-data sessions are correlated as a group of sessions.
 18. Thesystem according to claim 14, further comprising an intermediaryinterposed between the first and second communication devices, saidintermediary conducting a first P2P session with the first communicationdevice and a second P2P session with the second communication device,and wherein logic creates the globally unique correlation identifierutilizing the Call-ID, the From-Tag, and the To-Tag, wherein theintermediary forwards the Call-ID and the From-Tag to the secondcommunication device in the SIP INVITE message, and forwards the To-Tagto the first communication device in the SIP 200 OK message.
 19. Thesystem according to claim 14, wherein the first and second communicationdevices are configured to create the globally unique correlationidentifier for a group communication session utilizing a unique focalpoint identifier communicated to the first communication device by aconference factory while creating a conference.
 20. The system accordingto claim 19, wherein the first communication device is configured tosend the globally unique correlation identifier to all participants ofthe conference by including the globally unique correlation identifierin a REFER request transmitted by the first communication device to eachparticipant in a dial-in conference, and to a focal point in a dial-outconference.
 21. A first communication device for correlating differentend-to-end data sessions, said first communication device comprising: amapping unit; and a processor configured to cause the firstcommunication device to: send a SIP INVITE message to a secondcommunication device during establishment of a first end-to-end datasession between the first communication device and the secondcommunication device, wherein the first communication device isconfigured to include a Call-ID and a From-Tag in a Same-Session headerof the SIP INVITE message; receive from the second communication devicein response to the SIP INVITE message, a SIP 200 OK message including aglobally unique correlation identifier comprising the Call-ID, theFrom-Tag, and a To-Tag added by the second communication device touniquely identify the second communication device; store the globallyunique correlation identifier in the mapping unit, wherein the mappingunit is configured to map correlation identifiers to sessionidentifiers, the mapping unit being selected from a group consisting ofa correlation table, a hash function, and a mapping function; andutilize the stored globally unique correlation identifier to correlatewith the first end-to-end data session, a second, independent end-to-enddata session subsequently established by the first communication deviceor the second communication device.
 22. A second communication devicefor correlating different end-to-end data sessions, said secondcommunication device comprising: a mapping unit; and a processorconfigured to cause the second communication device to: receive from afirst communication device, a SIP INVITE message during establishment ofa first end-to-end data session between the first communication deviceand the second communication device, wherein a Same-Session header ofthe SIP INVITE message includes a Call-ID and a From-Tag; create aglobally unique correlation identifier by adding a To-Tag to the Call-IDand the From-Tag, the To-Tag uniquely identifying the secondcommunication device; send the globally unique correlation identifier tothe first communication device in a SIP 200 OK message in response tothe SIP INVITE message; store the globally unique correlation identifierin the mapping unit, wherein the mapping unit is configured to mapcorrelation identifiers to session identifiers, the mapping unit beingselected from a group consisting of a correlation table, a hashfunction, and a mapping function; and utilize the stored globally uniquecorrelation identifier to correlate with the first end-to-end datasession, a second, independent end-to-end data session subsequentlyestablished by the first communication device or the secondcommunication device.